How do PSN accounts and primary console work? [closed]

I just ordered a PS4 Slim and was wondering how PSN and primary console accounts work. I'm a PC gamer and I've never really touched a console, I mainly bought this PS4 for my SO since she can sometimes get bored during the (rare) longer sessions I spend in front of the PC. She enjoys "casual" games and said she prefers the PS4 controllers over the Xbox controllers. So here I am.

We have thought about what happens with the PS4 if we split up, obviously she gets it since I probably wont have much use for it but what happens to the games we buy? I basically only want Horizon Zero Dawn and I'll be dammed if she gets it if we split up for some reason. So how to the PSN accounts and games work?

I assume you need a PSN account to even use the console? So let's say she creates PSN account A and buys game A1 with her account. I then create PSN account B and purchase Horizon Zero Dawn. If I understand this correctly, I cannot play game A1 with my account (B) unless she sets our PS4 as her primary console on her account (A), is this right? The same goes for my account and Horizon Zero Dawn? If I set my account (B) to have our PS4 as its primary console then she can also play HZD or whatever game I purchase with my PSN account? And I know you can only have one primary console on your account but can a console be the primary console of multiple accounts?

Also, if I buy a game with my account (B) but don't download it then she can't download it with her account (A)? Even if the console is my primary console, only my account (B) can actually download the game? And do accounts have users or are you just logged in to your account? Say I log in with my PSN account, do I only have one user which is my actual PSN account or do I log in with my PSN account and then create a separate user for my account?

I hope I didn't lose you in the text but if I did, here is a TL;DR of my questions.

• A console can be the primary console of multiple PSN accounts?
• We can share games if we both set our console as primary on our PSN accounts?
• Do PSN accounts also have users or are you just logged in as your PSN account?
• If you have users under the same PSN account, I could just create a user under her PSN account instead of logging into my own PSN account if I wanna play a game she has? How do save files work in this scenario?
• Is it a hassle to switch between PSN accounts?

Q: A console can be the primary console of multiple PSN accounts?

A: Yes

Q: We can share games if we both set our console as primary on our PSN accounts?

A: Not sure what you mean by share games, but all profiles on a PS4 that is logged in to a PSN account have access to those games. If you mean can I play games of another PSN account just because that account and my account has the same primary console then the answer is NO.

Q: Do PSN accounts also have users or are you just logged in as your PSN account?

A: PSN account is just you logged in to your PSN accounts, user profiles are local.

Q: If you have users under the same PSN account, I could just create a user under her PSN account instead of logging into my own PSN account if I wanna play a game she has? How do save files work in this scenario?

A: User profiles are local and saved data is local only the games matter in terms of PSN accounts

Q: Is it a hassle to switch between PSN accounts?

A: It is very easy to switch between PSN accounts, just log off and log in with one button and type your new user name and password that you want change to, this can all be done within settings.

Of course all of these problems will be solved easily if you just buy a physical copy of the game, which can be played independent of a PSN account.